Generally, the WT1 protein-derived cancer antigen peptide is a partial peptide derived from human WT1 protein consisting of 449 amino acids (SEQ ID NO: 2), and is specifically a peptide consisting of 8-12 amino acids or a dimer thereof. It is presented to a major histocompatibility complex (MHC) class I antigen, and includes a peptide which is antigen-recognized by cytotoxic T cell (cytotoxic T-lymphocyte, hereinafter to be referred to as CTL). MHC in human is called human leukocyte antigen (HLA).
Among the WT1 protein-derived partial peptides, partial peptide consisting of the amino acid sequence shown by Arg-Met-Phe-Pro-Asn-Ala-Pro-Tyr-Leu (SEQ ID NO: 3) (WT1126-134 peptide) and modified peptide obtained by modifying the second amino acid from the N terminus of partial peptide consisting of the amino acid sequence shown by Cys-Met-Thr-Trp-Asn-Gln-Met-Asn-Leu (SEQ ID NO: 6) (WT1235-243 peptide) from methionine to tyrosine (i.e., peptide consisting of the amino acid sequence shown by Cys-Tyr-Thr-Trp-Asn-Gln-Met-Asn-Leu (SEQ ID NO: 5)) have been reported to be useful as peptides that bind to HLA to induce CTL (see patent documents 1-4). However, a modified peptide obtained by conjugating these two peptides via a disulfide bond between cysteine residues has not been known, and an optimal cancer vaccine composition therefor has neither been known.
On the other hand, among the WT1 protein-derived partial peptides, partial peptide consisting of the amino acid sequence shown by Trp-Ala-Pro-Val-Leu-Asp-Phe-Ala-Pro-Pro-Gly-Ala-Ser-Ala-Tyr-Gly-Ser-Leu (SEQ ID NO: 1) (WT134-51 peptide) by itself is useful as a peptide that binds to HLA to induce CTL, and it has further been reported that combined use with the aforementioned peptide provides effects as helper peptide (see patent document 5). However, an optimal cancer vaccine composition containing this peptide has not been known.
Since an optimal cancer vaccine composition containing WT1126-134 peptide and/or modified WT1235-243 peptide, and WT134-51 peptide is useful as a cancer vaccine, the development of a formulation ensuring stability of these peptides has been expected.